Vibrations of cracked reinforced and prestressed concrete beams

Abstract

The dynamic behaviour of bent reinforced concrete beams in elastic range is significantly influenced by cracks caused by former loads. Considering this fact a more accurate calculation of the eigenfrequencies of the beams is available. Experiments have shown that the features of vibration differ from the results obtained by the well-known linear model, if cracked zones exist. The cause of this phenomenon is that the bending rigidity of the cross-sections in the cracked range depends on the sign of the actual bending moment. Therefore the vibration shows non-linear characteristics in the elastic range as well. The dynamic behavior of bent prestressed concrete beams is similar. The dynamic characteristics of prestressed beams besides cracks is influenced also by the intensity and eccentricity of the axial force. For a detailed investigation of the problem, experiments and non-linear analysis were performed. On the basis of these the virtual eigenfrequencies of the non-linear vibrations were determined

Dynamic response of Two-DOF homogeneous dynamical systems

“…However, some qualitative predictions of the proposed theory are compatible with experimental observations. For example, sub-harmonic resonance peaks predicted by the theory have been observed in the frequency domain plots in same experimental investigations [8,51]. It should be realised, however, that the proposed theory itself suggests some new experiments for checking its validity.…”